A solid electrolytic capacitor element is usually composed of an anode body, and a dielectric layer and a cathode layer stacked in this order on the anode body. The cathode layer is usually composed of a semiconductor layer, a carbon layer and a silver layer stacked in this order on the dielectric layer. If the solid electrolytic capacitor element having a capacity set to a predetermined value is left for a long period before encapsulating with a resin or the like, the capacity may change. For example, the leaving for a long period increases a capacity of a solid electrolytic capacitor element using an anode body comprising tungsten, or the leaving for a long period decreases a capacity of a solid electrolytic capacitor element using an anode body comprising aluminum, tantalum or niobium. A great change in capacity is undesirable for electronic components in both cases of increase or decrease. The increasing of capacity is remarkable in a solid electrolytic capacitor element using an anode body comprising tungsten.
Techniques intended to decrease leakage current have been proposed. For example, Patent Document 1 discloses a solid electrolytic capacitor which comprises an anode body, a dielectric placed on the surface of the anode body, a conductive polymer placed on the surface of the dielectric, an insulating portion placed in an island shape on the surface of the conductive polymer, and a current collector placed on the surfaces of the insulating portion and the conductive polymer, wherein the insulating portion comprises at least one selected from the group consisting of alumina, an alumina hydrate, silica and a silica hydrate.
In addition, Patent Document 2 discloses a solid electrolytic capacitor characterized in that, the solid electrolytic capacitor comprises an anode member, and a dielectric layer, a solid electrolytic layer, a cathode lead-out layer and an outer shell resin layer placed in this order on the outside of the anode member; and further comprises a protective layer, made of a material mainly comprising an inorganic oxide, between the cathode lead-out layer and the outer shell resin layer.